Pulmonary compliance and air flow resistance

A method for measuring pulmonary flow resistance, the method comprising the steps of:

• (a) receiving, when a gas output port of a gas-tight chamber is closed and a patient is blowing into a gas inlet of the chamber at a given pressure, a measurement of a first pressure in the chamber from a pressure sensor, wherein a gas-flow path between the gas inlet and the gas output port has a first resistance value;
• (b) receiving, after step (a) has been performed, and when the gas output port is opened and the patient is blowing into the gas inlet so as to maintain the given pressure relatively constant, a measurement of a second pressure in the chamber from the pressure sensor and a measurement of a first gas flow through the chamber from a gas flow sensor;
• and
• (c) computing a first pulmonary flow resistance based upon the measurement of the first pressure, the measurement of the second pressure, the first resistance value, and the measurement of the first gas flow.

A method for measuring pulmonary flow resistance, the method comprising the steps of:

• (a) closing a gas output port of a gas-tight chamber, the chamber having a gas inlet;
• (b) setting a gas flow resistor disposed in a gas-flow path between the inlet and the outlet port to a first resistance value;
• (c) receiving, after step (a) and step (b) have been performed and when a patient is blowing into the gas inlet at a given pressure, a measurement of a first pressure in the chamber from a pressure sensor;
• (d) opening, after step (c) has been performed, the gas output port;
• (e) receiving, after step (d) has been performed and when the patient is blowing into the gas inlet so as to maintain the given pressure relatively constant, a measurement of a second pressure in the chamber from the pressure sensor and a measurement of a first gas flow through the chamber from a gas flow sensor;
• and
• (f) computing a first pulmonary flow resistance based upon the measurement of the first pressure, the measurement of the second pressure, the first resistance value, and the measurement of the first gas flow.

A device for measuring pulmonary flow resistance, the device comprising:

• a housing that defines a gas-tight chamber, the chamber having a gas inlet and a gas output port and a gas-flow path between the gas inlet and the gas output port, wherein the gas output port is configured to switch selectively between (i) an open position in which gas can flow out of the chamber through the gas output port and (ii) a closed position in which gas flow out of the chamber is blocked;
• a gas flow sensor configured to measure flow of gas through the chamber;
• a pressure sensor configured to measure pressure in the chamber;
• a gas flow resistor disposed in the gas-flow path, configured to be adjustable by a control input;
• and
• a controller configured to
• (a) set the gas flow resistor to a first resistance value by sending a first control signal to the control input,
• (b) receive, when the output port is closed and a patient is blowing into the gas inlet at a given pressure, a measurement of a first pressure from the pressure sensor,
• (c) determine, after steps (a) and (b) have been performed and when the gas output port is opened, that the patient is blowing into the gas inlet so as to maintain the given pressure relatively constant,
• (d) receive a measurement of a second pressure from the pressure sensor and a measurement of a first gas flow from the gas flow sensor while the patient is blowing into the gas inlet so as to maintain the given pressure relatively constant, and
• (e) compute a first pulmonary flow resistance based upon the measurement of the first pressure, the measurement of the second pressure, the first resistance value, and the measurement of the first gas flow.